Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
An optical device can be made up of a plurality of optical elements. For example, an optical device may be formed by combining a variety of optical elements including a light-emitting element such as a laser diode (LD) or a light-emitting diode (LED), a passive element such as a lens, a waveguide or a switch, and a light-receiving element such as a photo diode or a charge coupled device (CCD). Generally, such an optical device can be fabricated by mounting each optical element on a substrate. A mounting robot may be used for adjusting the optical axis of each optical element.
Recently, instead of mounting optical elements on a substrate individually, there is an interest in wafer-based mounting technology in order to improve efficiency of production. In the fields of semiconductor devices and micro electro mechanical systems (MEMS), a wafer-level packaging (WLP) technology has been developed. However, such technology cannot be simply applied to fabricate an optical device including optical elements. This is because it is difficult to satisfy optical axis adjustment precision at the sub-micron level in order to ensure the required optical properties over an entire wafer by the WLP technology. This is particularly difficult when an optical device is formed using more than one type of substrate, for example using a silicon substrate and a glass substrate.
The present disclosure contemplates that in order to establish wafer-level optical device mounting technology, it may be desirable to develop a mounting method with which the optical alignment precision can be easily ensured over the entire wafer.